Worlds Beyond the Sea of Stars

Plane travel, as it usually appears in D&D-like settings is not a component of the Sea of Stars but that does not mean that they do not exist on some form or another:

Worlds Beyond the Sea of Stars

After the gods were deposed and the world Sundered, access to the other worlds became exceedingly difficult. It is believed that the Empress sealed the worlds beyond away, while the gods who ruled them had been slain, many of their servitors survived, now impotently sealed away in their paradises and pits. The beings of the worlds beyond could still be brought though into the world by use of spells and rituals but rarely for long. The previously existing gates to the higher and lower worlds beyond were shattered and destroyed immediately after the Sundering as the dragons seized and plundered the churches and temples. Those that have opened pathways to such places have been able to cross over but none have ever returned.

The elemental realms remain closer to the Sea of Stars, there even being places where gates and rifts to them still exist. Thus, paragons and embodiments of the pure elements remain easier to access through various magics; some speculate that this is because the dragons themselves are aligned with the elements, others because the world is comprised of the elements and could not exist without them.

The shadow realm -that land between life and death- remains accessible and can be crossed into, usually by magic, though some gateways may remain. Unlike gates to the over and under worlds, the shadow gates were simply not a high priority and several may have been overlooked, lost or deliberately hidden.

Notes: My thoughts on the place of elementals in the Sea of Stars has evolved so there are no longer separate elemental planes, read more here.